Sunday, December 26, 2010

The Davis Mountains

Looking at a satellite map of the U.S., one notices a dark smudge in West Texas, north of the Big Bend area and just south of I-10. This dark terrain reflects the vegetation and rock formations of the Davis Mountains, which stand out against the pale, drier landscape of the Chihuahuan Desert.

Volcanic in origin, the Davis Mountains are remnants of two large calderas and their associated rhyolite lava flows, ash tuffs, cinder cones and laccolith formations. Persisting for 10 million years, the volcanic activity began in the Oligocene, some 35 million years ago, when grasslands were evolving across the Great Plains and mammalian megafauna dominated the scene. The Davis Mountains cover much of Jeff Davis County and represent the most extensive mountainous region in Texas; summits range from 3500 to almost 8400 feet. Like the Chisos Mountains of Big Bend National Park, the Davis Mountains are part of the Trans-Pecos Volcanic Field, which extends across West Texas and into Northern Mexico.

Catching upslope moisture from all directions, these mountains receive about 18 inches of precipitation each year, more than double that of the surrounding desert. For this reason, they support mixed woodlands of oak, juniper and pine, attracting a large variety of birds, mammals and other wildlife.